Catheter heads, including those of the type mentioned above, are, for example, used in conjunction with infusion means in order to enable a part of the catheter head—i.e., the cannula casing together with a cannula inserted in a body—to be changed or a fluid to be exchanged. This useful for a patient to whom a fluid is permanently or repeatedly administered. To this end, another part of the catheter head—the connecting element to a fluid supply—is detached from the cannula casing and, once the cannula casing has been exchanged, can be placed onto the new cannula casing attached to the body in order to continue introducing the fluid. At the same time, a new fluid container can easily be connected to the connecting element. It is also possible to place another, homogeneous connecting element of a new fluid container onto the cannula casing, such that the fluid can continue to be administered. Such a catheter head can however also be used for example to remove analysis liquid from a patient's body or to introduce the analysis liquid into the body and remove it again.
In general, the cannula casing of the catheter head comprises a cannula which protrudes from one side of the cannula casing and a passage channel running through the cannula casing and connected to the cannula. The connecting element of the catheter head has a fluid supply and is connected to the cannula casing in such a way that the fluid supply is connected to the passage channel. Furthermore, a guiding means is provided which, when the cannula casing is combined with the connecting element, guides the connecting element into the correct position onto the cannula casing. The connecting element is firmly fixed on the cannula casing by a fixing means, but can be detached again.
Such a catheter head is, for example, described in DE 299 05 068 for a subcutaneous infusion means. In this catheter head, the connecting element is plugged into the cannula casing, such that the fluid supply is arranged as an extension of the cannula. The guiding means and the fixing means is then axially symmetrical with respect to the longitudinal axis of the fluid supply. A first part of the guiding means is provided in the cannula casing as a hollow space having a circular inner wall. A second part of the guiding means is provided by an outer wall of the connecting element which during combining abuts the inner wall of the hollow space in the cannula casing. Once the cannula casing has been combined with the connecting element, the connecting element is therefore rotatably arranged in the cannula casing. A blocking mechanism is provided which fixes the connecting element in a certain angular position with respect to the casing. In each of these angular positions, however, the fluid supply forms the extension of the cannula. Different angular positions between the cannula and the fluid supply are not formed. Such a blocking mechanism is provided, for example, by a flexible sealing arm provided on the connecting element together with an exterior protrusion. Once the connecting element has been inserted into the cannula casing, the protrusion engages with a circular groove in the interior of the cannula casing and in this way fixes the connecting element to the cannula casing. In order to release the block, the flexible sealing arm is bent inwards and the connecting element can be removed from the cannula casing.
A catheter head can comprise a plate-shaped cannula casing with a cannula protruding downwards, as is known from U.S. Pat. No. 6,017,328. A connecting element, also plate-shaped, is placed onto the cannula casing in such a way that the fluid supply is arranged substantially perpendicular to the axis of the cannula. The fixing element comprises two laterally running arms which can be pressed together towards the center of the fixing element. At their ends, the arms comprise protrusions directed towards the cannula casing, via which they firmly engage with corresponding cavities on the cannula casing. The engagement can be released again by pressing the arms together. The angular position of the connecting element with respect to the cannula casing is defined by the predetermined position of the cavities on the cannula casing. The direction in which the fluid supply leads away from the cannula casing is therefore predetermined.
In the catheter heads as set forth in the prior art, it is either not possible to select an angular setting between the cannula casing or cannula and the fluid supply, or a particular angular position is pre-set and not variable. If, therefore, it is desired for the fluid to be supplied from another direction, one exemplary solution is to select a supply tube having a sufficiently large length, which can be bent to the desired other direction without disrupting the flow, or, in the case of a cannula remaining in the patient, the entire catheter head has to be rotated, which is unpleasant and unacceptable for the patient.